Described herein is a method for providing a carrier material comprising a nonwoven layer of fibers and threads extending in longitudinal direction of the carrier material.
Carrier materials comprising a nonwoven layer fibers are being used in many applications such as for example bitumen roofing membranes, roofing underlayment sheets and (cushion) vinyl floor coverings.
Elevated temperatures and/or high tensions encountered in production processes may require the addition of threads, in particular high modulus threads such as for example glass yarns, in the longitudinal direction of the carrier material to withstand the high tensions in machine direction during processing, especially at elevated temperatures. Such carriers are well known, for example from EP1372951, and are generally produced by introducing a number of individual threads, preferably spaced apart at regular distances, in the nonwoven layer of fibers, either directly during the formation of the nonwoven layer of fibers or by laminating individual threads to a prefabricated nonwoven layer of fibers.
EP0239207 A2 discloses a method for manufacturing a papermaker's felt using a low melting scrim to which a batt is needled, followed by a heat treatment.
However, the introduction of large numbers of individual threads is a rather complex process, requiring a large creel to unwind the individual threads from bobbins. When the individual threads are introduced in the nonwoven layer of fibers directly during the formation of the nonwoven layer of fibers, the production efficiency is negatively influenced by interruptions both in the formation of the nonwoven layer of fibers and in the introduction of the individual threads.
Furthermore, to ensure that the individual threads extending in longitudinal direction remain spaced apart at regular distances, the tension on each individual thread has to be controlled to the same level thus posing high demands on process control during unwinding of the individual threads.
There thus remains a need for an improved process for providing a carrier material comprising a nonwoven layer of fibers and threads extending in longitudinal direction of the carrier material.